Seasonal dynamics of Cu2+, Zn2+, Ca2+, and Mg2+ in gonads and liver of winter flounder (Pseudopleuronectes americanus): evidence for summer storage of Zn2+ for winter gonad development in females

Abstract

The concentrations and total amounts of Zn2+, Cu2+, Mg2+, and Ca2+ were measured in the gonads and livers of sexually mature winter flounder caught at approximately monthly intervals in Chapel's Cove, Newfoundland.The winter flounder fed from April through to October each year. Male and female gonads initiated development in August and spawned in June. The maximum testes weight was observed in October corresponding to the end of the feeding period. The maximum ovary weight was not observed until February, indicating that considerable ovarian growth occurred after feeding had stopped.All four metals in the gonads and livers exhibited seasonal changes. The ovaries accumulated four to six times more Zn2+, Cu2+, and Ca2+ than did the testes. The testes accumulated more Mg2+ than did the ovaries during annual development. The ovaries continued to incorporate all four metals after the fish had stopped eating. Some of the ovaries postfeeding requirements for Zn2+ and Cu2+ could have been met by utilizing liver stores. However, most of the ovaries requirements for Zn2+ must have been obtained from other storage areas in the fish. The ovaries postfeeding requirements for Cu2+, Ca2+, and Mg2+ could have been obtained by the flounder absorbing these metals from the seawater.